shaman king
Soul eater, when they split from soul eaters original manga line i was kind of shocked. In the end the story they created with the anime was complete shit, and a total waste of time. If you have watched it then you know what i am talking about. For those that want to watch it dont, save yourself and read the manga.

Shugo Chara-Ikuto was supposes to go on a dat ewith Amu and confess to her when he left and the filler episodes are killing me!
Fruits Basket-So many characters who aren't there!
FMA-The ending was sad!
Vampire Knight-They messed up the Yuuki and Zero ending scene